Aircraft undercarriage



jufiy 2, 1953 R. w. BROWN AIRCRAFT UNDERCARRIAGE 2' Sheets-Sheat 1Original Filed Feb. 18, 1947 INVENTOR. BY

y 1953 R. w. BROWN AIRCRAFT UNDERCARRIAGE 2 Sheets-Sheet 2 I OriginalFiled Feb. 18, 1947 U 8 R M w m 1 w M m W j 1 IX Hm v i 4 a I DA 0 a m wMum 8 w 5 m w a ,m I I n Patented July 28, 1953 AIRCRAFT UNDERCARRIAGERoy W. Brown, Akron, Ohio, assignor to The Firestone Tire & RubberCompany, Akron, Ohio, a corporation of Ohio Original applicationFebruary 18, 1947, Serial No. 731,590, now Patent No. 2,581,935. Dividedand this application October 20, 1951, Serial No.

8 Claims. (Cl. 244-103) This invention relates to aircraft undercarriageespecially adapted for cross-wind landings.

One of the problems to be considered in the design and development ofsmall, privately owned aircraft is the lackof adequate landing strips topermit safe landings under all wind conditions. It is quite desirable tohave the aircraft adapted for cross wind landings so that only a minimumof'landing strips and areas will be required to permit the aircraft toland regardless of the prevailing wind conditions.

While attempts have been made to provide aircraft with undercarriagesthat facilitate crosswind landings, such equipment has been too heavy,or quite costly, or has been otherwise objectionable.

The general object of this invention is to avoid and overcome theforegoing and other disadvantages of previous typesof aircraftundercarriages and to provide an aircraft undercarriage characterized byits ability to effect controlled swivelling of one or more of thelanding wheels during cross-wind landings.

Still another object is to provide resilient torsional restraint of aswivelled landing wheel for aircraft.

Another object of the invention is to limit the amount of swivellingmovement of a landing wheel relatively to the aircraft structure.

A further object of the invention is to provide an aircraftundercarriage which requires a.

minimum of maintenance and is adapted for long service life.

'Another object of the invention is to provide anaircraftundercarriagecomprising a landing wheel which may be torsionallydeflected to guide the aircraft and which will return to a neutralposition automatically when the torsional force thereon is removed.

Another object is to provide an improved rubber torsion member. 7

The foregoing and other objects of the invention will be made apparentas the specification proceeds.

Reference now is made to the accompanying drawings, wherein:

Fig. 1 is an elevation of an aircraft undercarriage embodying theinvention;

Fig". 2 is an enlarged horizontal section taken I on line 2-2 of Fig. 1;

Fig. 3 i a vertical section taken on line 3-3 of Fig. 2; I

Figs. 4, and 6 are fragmentary vertical sections taken on lines 4-,-4,55 and 6-6 of Fig. 2;

1 Fig. 7 is an. enlarged sectional view taken on line 22 of Fig. l butshowing another embodiment of the invention; and

Fig. 8 is a fragmentary vertical section taken on line 88 of Fig. 7.

Now referring in detail to the structure shown in the drawings, asupport member 20, usually tubular in form, is provided, which member ismade from any suitable material and is adapted to engage in aconventional manner with a support plate I! of an aircraft for supportof same when not in the air. Member 2|] is adapted to slidably receivecylindrical member 2|, the lower end of which carries a torsion member22 to provide pivotal mounting for a pair of fork arms between which apneumatic tire and wheel assembly I9 is journalled.

Vertical load is transmitted between member 20 and cylinder 2| by meansof a radially extending flange 23, suitabl secured, as by welding, tocylinder 21. A flange 24 is usually formed on the lower end of themember 20 and a suitable annular thrust bearing 25 is positionedintermediate flange 23 and flange 24. Thrust bearing 25 may be of anysuitable construction and, in this instance, is shown as comprising arubber member having a friction material coating 26 on its lowersurface, or extending through the body of the member 25, as shown, todivide the bearing, if desired. The friction material coating 26 has theunusual property of greater kinetic friction than static friction and itis made from fabric which is impregnated with castor oil, a.

' wax compatible with the oil, and aluminum soap.

Graphite also may be present in the impregnating composition, which isthixotropic. A conventional split clamp ring 21 is provided to engagewith the outer surfaces of the flanges 23 and 24 to limit axial movementbetween members 20 and 2! while permitting rotation therebetween.

In order to retain the telescoped portions of the members 20 and 21 inconcentric alignment, suitable bearings 28 and 29 are positioned withinthe cylindrical space therebetween. The bushings 28 and 29 areconstrained against axial movement by metal backing plates 3| and 32,respectively, integrally bonded thereto, and expanded to form an annularrib at 33 and 34, respectively, said ribs being complementally engagedin suitable channels provided in member 20 by crimping. Ribs 33 and 34may be replaced by a series of circumferentially spaced expanded areas,if desired. Friction material 30, similar to the friction material 26,may be inteof suitable metal, is adapted to resist, resiliently,relative rotational movement between the mem-.

bers 20 and 2I and to realign such members upon removal of a distortingforce.

In order to limit the amountof relative arcuate movement of thepneumatic tire and wheel assembly I9, associated with cylinder 2!, stopor motion limiting means may be provided. In Figs. 2, 4, 5 and 6 thereis shown one embodiment of means for limiting rotational or casteringmovement of the undercarriage wheel disclosed. herein. A stop lug I27,finding its support in member 20, is positioned immediately above flange24 to depend therefrom, the lower margin thereof extending into acut-out section I28 of clamp 21, as shown in Fig. 2. The split clamp 21preferably has two such cut-out sections I28, diametrically opposed andeach adapted to receive a stop lug. The remainder of the C-clamp 21 iscontinuous around each semi-circular portion of member 20 for retentionof flanges 23 and 24 and bearing 25 in unitary assembly. Stop lugs I2'Iabut the end margins of cut-out sections I28 to limit wheel castering ineach direction. Cutout sections I28 are of preselected length to controlthe desired limit of castering. More than one set of cut-out sectionsmay be provided in the same assembly to provide universal application ofthe undercarriage unit.

The construction described hereinabove provides a compact, sturdy,effective means for permitting wheel castering in aircraft undercarriagewhile simultaneously damping such castering to prevent wheel shimmy oryaw. Controlled castering enables the aircraft to be safely landed atgreater angles to the prevailing wind than can be safely efiected withprevious undercarriages. Upon landing, initial ground contact of thewheels automatically aligns the wheels in the direction of forwardmotion of the airplane and this is true even though the airplaneapproaches the runway in a side-slip, due to the well-knowncharacteristic of a caster to automatically align a wheel in thedirection of vehicle movement, with the wheel axis tailing the verticalcaster pintle.

The invention uses a minimum of parts and comprises an aircraft mountedcylinder 20 I and a wheel carrying cylinder 2! in telescoped relationtherewith. Said cylinders are held in spaced concentric alignment by anannular friction or torsion member I of the type set out and describedin detail in my prior Patent 2,581,935 dated January 8, 1952 of whichthis application is a division. Reference is made to said patent for adetailed description of the character of said member I. The cylinders 20and 2I are, in general, secured together and associated for relativerotational movement and load transmittal as in the embodiments of theinvention described in my said patent. In this instance, a bridge member82 is secured within the cylinder 20 and a support plate 83 is securedto the cylinder 2|. The bridge member 02 and the plate 83 havenon-circular apertures 8-4 and 85 formed therein complementally toreceive ends 86 of a torsion bar 81 positioned by the bridge plate 82and plate 83 and extending therebetween. Torsion bar 81,

4 of suitable metal is adapted to resist, resiliently, relativerotational movement between the members and 2| and to realign suchmembers upon removal of a distorting force.

A modification of the invention embodying use of a torsion bar is shownin Figs. '7 and 8. In

this embodiment, cylinder 2I extends into tubular member 20 and ismounted therein for slight arcuate movement with relation to the member20 any conventional manner. An annular bushing 28 is disposed betweenmembers 2I and 20 andv functions as a bearing to keep these members inconcentric alignment. Bushing 28 is of the same character as bushing 29referred to in the discussion above relative to Fig. 2. A bridge member93 is positioned in and secured to the cylinder 20 and such bridgemember 93 has an aperture 94 therein which engages with head 95 shapeand spaced circumferentially. Cam surlight weight but sturdyconstructions.

faces 91 are adapted to engage with rollers 58, which are mounted on ayoke member 99, by pins I-0I. Fig. 15 best shows that the cam surfaces97 are substantially symmetrically formed and have one maximum recessedor cut-out portion which gradually slopes up to the end of the cylinder2|. The rollers 98 normally are positioned at the bottom of the camsurfaces 91. To insure the requirement of substantial force for movementof the cams up the cam surfaces 91 to the intrevening flat, a relativelyheavy coil spring I02 is compressably retained between bridge member 93and the yoke 99. Hence in this embodiment of the invention, relativerotational movement between the cylinder .2I and the tubular member 20is resisted both by torsional forces set up in the torsion bar 96 and bythe force required to compress spring I02 the axial depth of cam 91. Inthis instance, the cams and their associated means function as springloaded detents that aid in centering the supported member 2I withrelation to the support member 20 and in resiliently resisting relativerotational motion therebetween due to wheel castering. Energy stored inthe spring I02 and torsion member 96 aids in returning the members 2Iand 20 to their neutral positions, upon release of wheel torque.

In the embodiments of the invention disclosed herein, any conventionalmaterial may be used in forming the aircraft undercarriage, theresilient or rubber-like bushings I and 2 used in the invention, thetorsion bars, etc. The illustrated embodiments are particularly adaptedto The advantages above enumerated for landing operations are equallyapplicable to take-01f operations, since the undercarriage describedherein enables an aircraft to move on the ground with the longitudinalaxis of the plane at an acute angle with the direction of ground motion.The carriage will function automatically as above stated to assume theproper wheel direction immediately upon ground contact during landing,regardless of whether the airplane is in straight flight or in asideslip, and the wheels will gradually return to normal or centeredpositions as the aircraft speed falls below the stall speed thereof. 7

In accordance with the patent statutes, one complete embodiment of theinvention has been illustrated and described in detail but the inventionis not limited to the specific examples set forth since modification maybe resorted to Within the scope of the appended claims.

What is claimed is:

1. In an aircraft undercarriage, two generally cylindrical supportmembers of unequal diameter positioned in telescoped relation, a torsionbar positioned along the axis of said support members with one endsecured to one of said support members and the other end secured to thesecond support members, a bridge member secured within the larger ofsaid support members and engaging an end of said torsion bar, a dishedcam surface formed on the axially inner end of the smaller of saidsupport members, a cam roller fioatably mounted within said largercylinder and engaged with said cam, and spring means compressivelyretained between the bridge member and cam continuously to urge said camroller into engagement with said cam surface, whereby rotationalmovement of one cylindrical member in respect to the other moves saidcam roller along the dished surface to eifect axial displacement of saidroller and compress or release tension on said spring.

2. In an aircraft undercarriage, two relatively rotatable memberspositioned in concentrically spaced telescoped relation, one of saidmembers being adapted to engage with an aircraft and the other of saidmembers being adapted to carry an aircraft wheel, an elongate metallicconnecting element, means securing one end portion of said connectingelement to one of said telescoped members, and means securing the secondend portion of said connecting element to the other element, and anannular friction element interposed between said members, said elementhaving a greater dynamic than static coefficient of friction, wherebyrelative rotational movement between said telescoped members isresiliently resisted by both said connecting element and said frictionelement.

3. An aircraft undercarriage as in claim 2, wherein the means securingone of the rotatable members to the connecting element permits relativeaxial movement while preventing rotational movement therebetween.

4. An aircraft undercarriage as in claim 2, wherein means are providedfor limiting the amount of relative rotational movement between thetelescoped members.

5. An undercarriage as in claim 2 wherein a stop lug is secured to onetelescoped member and a stop member is associated with the other of saidtelescoped members to limit relative rotational movement therebetween.

6. In an aircraft undercarriage, two generally cylindrical supportmembers of unequal diameters positioned in telescoped relation, at leastone resilient support member interposed axially between the cylindricalsupport members, a torsion bar passing through said resilient supportand being along the axis of said cylindrical members with one endsecured to one and the other end to the other cylindrical supportmember, a cam surface associated with an end of one of the cylindricalsupport members, a cam follower associated with the other cylindricalsupport and being adapted to cooperate with said cam surface, wherebyrotational movement of one cylindrical member in respect to the othermoves the cam against or away from the cam surface and effects relativeaxial movement of the cylindrical supports and increases or releasestension in said resilient member.

7. In an aircraft wheel mounting, two relatively rotatable memberspositioned in telescoped relation, a torsion member in the form of arigid rod, 3, bridge member secured to one of said members and engagingan end of said torsion rod, and means associated with the other of saidsupport members for engaging the second end of said torsion rod wherebyrelative rotational movement of said telescoped members is torsionallyresisted by said rod.

8. In an aircraft wheel mounting, two relatively rotatable tubularsupport members positioned in telescoped relation, a connecting torsionrod, means securing one end of said connecting rod to one of saidmembers, and means securing a second portion of said connecting rod tothe other member whereby relative rotational movement of said telescopedmembers is torsionally resisted by said connecting member.

ROY W. BROWN.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 395,147 Jeifery Dec. 25, 1888 2,472,415 Geisse June '7, 19492,581,935 Brown Jan. 8, 1952

